Error in maps: data quality and fitness for use

Error (mathematically) is the difference between a measured quantity and its "true" value
(figuring out what is true is often not completely obvious...)
Maps can be tested by: internal evidence (repeated measurement), comparison to source,
or comparison to an INDEPENDENT source of HIGHER accuracy

Distinction between precision (resolution of numbers, tightness of internal distribution) and accuracy (relationship to geographic entities, ability to replicate, etc.)

Components of Data Quality recognized by National Standard for Digital Data Quality

• Lineage

• POSITIONAL ACCURACY

• ATTRIBUTE ACCURACY

• LOGICAL CONSISTENCY

• COMPLETENESS

Last four (IN CAPS) are testable, Lineage is not...)

Metadata Standard: another way of expressing the same things

Although the scheme above was adopted in a formal standard (as SDTS, ANSI/NCITS 320.1998), FGDC also adopted the Content Standard for Metadata, which is in more practical use.

• schematic organization: basic parts. a colorized version of the text.
• the Data Quality section is essentially similar to SDTS.

Resources on Accuracy

Standards on geopositional accuracy:

• Reporting standards
• Geodetic Networks
• What used to be called the National Map Accuracy Standards, [also in its simple glory] now rendered somewhat more statistically valid, and more consistent with geodetic positioning: National Standard for Spatial Accuracy.

upcoming course: Winter 2004, Geography 458 Map Sources and Errors.